Acta Physicae Superficierum • Vol ? • 200? THEORETICAL ANALYSIS OF STM SPECTRA IN CUPRATE AND PNICTIDE SUPERCONDUCTORS ANNA CIECHAN, JAROMIR KRZYSZCZAK, KAROL IZYDOR WYSOKI ´ NSKI Institute of Physics and Nanotechnology Centre, M. Curie - Sk lodowska University, 20-031 Lublin, Poland Our recent approaches [1] to rationalise the spectra obtained by means of the scanning tunelling spectroscopy (STM) for high temperature cuprate and pnictide superconductors (HTS) have been presented. The experimental STM data on cuprates [2] and pnictides [3] both show the existence of intrinsic electronic inhomogeneities. They are very large in cuprates and by the factor of two smaller in pnictides. It is interesting to note that both systems share a number of other similarities: e.g. layered structure and antiferromagnetic state of undoped parent compounds. They also differ in few important aspects: while cuprates are essentially one - band systems the pnictides have many bands at the Fermi energy; also the gap symmetry seem to be different. The gap of cuprate HTS has d -wave symmetry and that of pnictides seem to be of s or s * (extended s-wave) symmetry without nodes, but with different phases at different Fermi surface sheets. The aim of the work is to use appropriate models and study the local properties of both classes of materials in order to shed light on possible meaning of similarities and differences. The approach we are using is a real space formulation of the theory of su- perconductivity [4] and numerical solution of the resulting Bogolubov-deGennes equations on small clusters [1]. We use the random boson-fermion model with in- teractions supporting d-wave symmetry to calculate the local spectra of cuprate superconductors and impure two band model with s-wave order parameters in both bands for description of pnictide materials. Figure (1) shows the example of the local density of states as a function of energy (bias) calculated at the sites of our samples along the line x=const. The left panel is for one band two-component model with random boson energies and